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Linux/TPS65273V: Does this DCDC determines startup voltage and updates VOUT_SEL accordingly by itslef?

wrymarki
Prodigy 155 points
Part Number: TPS65273V

Tool/software: Linux

Hi,

I use in my reference hw  tps65273V  power regulator which is initially configured by resistors to select proper startup voltage. The issue I have with this chip is that seems like it does not determine startup voltage and sets VOUT_SEL reg properly so later when OS boots and driver is probed the driver sees the actual voltage selector and not the minimum supported that is 0.68V. 

I cannot see anything in the datasheet to confirm this is the expected behaviour and I should explicitly update VOUT_SEL with an initial value (startup voltage) somewhere in a boot code. Also, cannot find any info if this chip has any circuit to determine start-up voltage. 

Q: Should TPS65273V determine startup voltage by itself, so I can read out startup voltage from vout_sel reg?

FYI, I run Linux on my reference board.

/Waldek

  • 0
    TI__Genius 15135 points

    Hi, Waldek

    Could you send the TPS65273V schematic to me? i want to review it.

  • 0 in reply to Zhao Ma
    Prodigy 155 points
    Hi,

    Here you can find datasheet and user guide for tps65273V www.ti.com/.../technicaldocuments
    Not sure if you are asking for schematic of tps65273V or my reference hw schematic where tps65273V is incorporated in?

    /Waldek
  • 0 in reply to wrymarki
    TI__Genius 15135 points
    Hi,
    I want to check your reference hw schematic.
  • 0 in reply to Zhao Ma
    Prodigy 155 points
    Hi,

    Need to check if I can share anything first. Anyway, I guess you can answer without schematic if I should expect or not actual startup voltage set in VOUT_SEL when it boots?

    I did not work much with power regulators so not sure if that is typical to this chips to initialize a register with startup voltage for example in the bootloader.

    /Waldek
  • 0 in reply to wrymarki
    TI__Genius 15135 points
    Hi,

    I checked on EVM.
    During power up, the Vout is determined by feedback resistor divider, using the equation in page 22 can calculate Vout value.
    After startup, you need to set bit 7=1 for Vout1_SEL and Vout2_SEL to enable I2C control, then the Vout will be set to min value 0.68V (default).
  • 0 in reply to Zhao Ma
    Prodigy 155 points
    Thanks for confirmation. This is what I see on my HW as well and that measn that likely booloader has to init tps register with the actual voltage set by feedback resistor devicder. Many thanks.
  • 0 in reply to wrymarki
    Prodigy 155 points
    I was thinking on this and it does look as very unusual.

    Wondering if that is intentional "Vout will be set to min value 0.68V (default)." and common to all TI power regulators to have a register readback option and not to determine and store the actual voltage. It's very misleading if you configure a startup voltage with bias resistors and next in SW you readback completelly different value. Data sheet does not mention that you have to init registers first which is still weird you have to do so.
  • 0 in reply to wrymarki
    TI__Genius 15135 points

    Hi,

    Sorry for misunderstanding, i will advise to revise the datasheet.

    My understanding:

    During power up, because of POR, all registers are reset, by default, the Vout is determined by bias resistors.

    If you want to set Vout by VID, you have to init registers first after power up.

    BTW, This part only provide the register readback, not provide actual voltage readback.